LLVM ERROR: Symbols not found: { ccall_PyByteArray_Type_105607, ccall_PyTuple_Type_105595, ccall_PyList_Type_105613 }

I'm trying to create a sysimage that includes `PyCall`.

Julia v1.5.4
PyCall v1.92.3

The build runs in an Ubuntu 18.04 docker container (it's part of the docker build process).

The sysimage creation goes on for about 96 seconds, and then fails with this error:

```
LLVM ERROR: Symbols not found: { ccall_PyByteArray_Type_105607, ccall_PyTuple_Type_105595, ccall_PyList_Type_105613 }
```

More output:
```
13:47:18 #74 63.50 [ Info: PackageCompiler: creating system image object file, this might take a while...
13:48:53 #74 159.0 LLVM ERROR: Symbols not found: { ccall_PyByteArray_Type_105607, ccall_PyTuple_Type_105595, ccall_PyList_Type_105613 }
13:48:53 #74 159.0
13:48:53 #74 159.2 ERROR: LoadError: failed process: Process(`/julia-1.5.4/bin/julia --color=yes --startup-file=no '--cpu-target=generic;sandybridge,-xsaveopt,clone_all;haswell,-rdrnd,base(1)' --sysimage=/julia-1.5.4/lib/julia/sys.so --project=/home/ubuntu/.julia/environments/v1.5 --output-o=/tmp/jl_ulcCLp.o -e '....
```

The strange thing is that it doesn't happen every time I run it. I've tried it maybe 6 times, and it fails about 50% of the time.

If it's any help, I recently upgraded from 1.92.2 to 1.92.3 but I didn't see anything in the diffs that could cause this.

Start by reproducing sysimage creation with Julia v1.5.4, PyCall v1.92.3, and the Ubuntu 18.04 Docker environment, recording whether the LLVM symbol failure is intermittent. Compare successful and failed runs around PackageCompiler and PyCall initialization. Done means the reported symbols are resolved and sysimage creation completes reliably.

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